login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A016113 Numbers whose square is a palindrome with an even number of digits. 4
836, 798644, 64030648, 83163115486, 6360832925898, 69800670077028, 98275825201587, 6819209882215742, 40447213778058769, 633856150760638652, 795559265009384106, 637323988797048057098, 3823177109095314778621 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Further terms, listed on P. De Geest's page, are  722956456358957313434535, 831775153121251039203514, 4275548277509699161443659 and 64897400105515621177314682. - M. F. Hasler, Jun 08 2014

REFERENCES

C. Ashbacher, More on palindromic squares, J. Rec. Math. 22, no. 2 (1990), 133-135. [A scan of the first page of this article is included with the last page of the Keith (1990) scan]

LINKS

Table of n, a(n) for n=1..13.

K. S. Brown, On General Palindromic Numbers

P. De Geest, Palindromic Squares

P. De Geest, Subsets of Palindromic Squares

M. Keith, Classification and enumeration of palindromic squares, J. Rec. Math., 22 (No. 2, 1990), 124-132. [Annotated scanned copy]

F. Yuan, Palindromic Square Numbers, as of July 2002.

PROG

(PARI) is_A016113(n)={vecextract(n=digits(n^2), "-1..1")==n&&!bittest(#n, 0)} \\ This is faster (than first checking for even length) if applied to numbers in a range where the squares are known to have an even number of digits (as should be the case for a systematic search). M. F. Hasler, Jun 08 2014

CROSSREFS

Cf. A027829. A proper subset of A002778.

Sequence in context: A235288 A162945 A138850 * A177846 A167603 A284187

Adjacent sequences:  A016110 A016111 A016112 * A016114 A016115 A016116

KEYWORD

nonn,base

AUTHOR

Robert G. Wilson v

EXTENSIONS

2 new terms were recently found by Bennett from UK (communication from Patrick De Geest).

Edited by M. F. Hasler, Jun 08 2014

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified January 22 22:34 EST 2018. Contains 298093 sequences.